The properties and characterization of Ti-6Al-4V alloy powder prepared by gas atomization by electrode induction melting

Titanium alloy has high specific strength, corrosion resistance, good biocompatibility and other excellent properties, which make it widely used in aerospace, chemical navigation and biomedical fields. However, the low thermal conductivity, low specific heat, low elastic modulus and high chemical activity of titanium alloy make it difficult to be machined, so the manufacturing technology of direct near-net forming has obvious advantages in the field of titanium alloy processing.

Additive manufacturing technology has developed rapidly in recent years, and its forming characteristics make it have special requirements for raw materials. Spherical powder with high density, good fluidity and easy to spread is an ideal raw material for additive manufacturing. ASTM F3049 standard provides specifications for 3D-printed metal powders. Powders with high sphericity, good fluidity, low oxygen content and narrow particle size distribution range are most suitable for additive manufacturing technology. The property of alloy powder plays an important role in the process and final property of additive manufacturing. The development of low cost and high quality powder preparation technology is the only way to spread additive manufacturing.

1) The best process for preparing Ti-6Al-4V alloy powder using EIGA atomization equipment is: annular slot nozzle, atomization pressure is 5 MPa, power supply is 25 kW.

2) Ti-6Al-4V fine alloy powder prepared by the best atomization process using The EIGA method has a concentrated particle size distribution and presents an approximate normal distribution. D10, D50 and D90 are 19.4, 31.9 and 51.5um respectively. The granule shape was relatively regular, the average roundness of powder was 90.6%, the average obtuse of Occhio was 92.7%, and the sphericity was higher. The vegetative index is low, and the satellite powder is not serious. Theoretically, it has good fluidity and loose loading density, so it is suitable for SLM forming.

3) Due to the inhomogeneous nucleation of the primary phase, the powder is composed of acicular LA martensite with different orientations. The chemical composition of the powder is stable and basically the same as that of the bar raw materials. The oxygen content is 0.12%, which is higher than that of the raw materials, but still meets the requirement of oxygen content for SLM forming.

4)SLM forming samples have a density of more than 99%, a lower surface roughness, a roughness Ra of 4.98um, and a microhardness of HV0.5 of 3525MPa.